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Pennsylvania Fracking Accident: What Went Wrong

Tuesday night, a natural gas pipe in Pennsylvania sprung a leak and sent thousands of gallons of chemical-laced water flowing out beyond its protective berms. The leak now appears to be under control, but PM explains how fracking operations normally collect the wastewater from their wells—and what went wrong this time.

A Pennsylvania gas well operated by Chesapeake Energy erupted late Tuesday, sending thousands of gallons of chemical-laced and highly saline water spilling from the drill site, heading over containment berms, racing toward a tributary of a popular trout-fishing stream and forcing seven families nearby to temporarily evacuate their homes. It's the latest and possibly the most serious fracking accident in the controversial seven-year hunt to unleash natural gas from the Marcellus Shale, the biggest natural gas fracking target in the U.S., which underlies large parts of Ohio, Pennsylvania, West Virginia and New York. The Pennsylvania Department of Environmental Protection (DEP) believes the cause of the accident—which occurred almost exactly a year after the BP rig explosion in the Gulf of Mexico— was apparently a double dose of bad luck: mechanical failure coupled with bad weather.

The leak happened at the Atgas 2H well in rural Leroy Township, about 175 miles northwest of Philadelphia. According to state and company officials, the failure occurred late Tuesday night when Chesapeake was in the middle of a "frack job." The controversial practice, essential to the extraction of gas from shale, involves pumping up to a million gallons of water treated with biocides, lubricants, surfactants and stabilizers a mile or more into the ground at pressures exceeding 9000 psi. Officials investigating the leak believe they have pinpointed the initial cause of the accident: A steel coupling located beneath the well's blowout protector, but above ground, appears to have failed, allowing thousands (and perhaps tens of thousands) of gallons of contaminated water to gush out of the well. (The blowout protector is the same technology as device that failed in the case of the BP oil spill. It didn't fail here, but if it had, both natural gas and water would have spewed forth from the well. However above-ground wells are much easier to shut down than those deep underwater.)

There were no injuries to the crew, no explosions, and no methane was released into the air, which would have happened in the case of a blowout. But there was also no way to immediately shut off the flow of water. And there was a lot of water.

Marcellus wells typically regurgitate between 30 and 50 percent of the water pumped into them. In normal circumstances, it comes back in a manageable flow, and the well operators collect it in pits or tanks. In some parts of the country that waste water would then be injected deep underground. But in Pennsylvania, the geology is not suited for deep-well injection, and so the water is kept in pits and tanks where it is treated to remove chemicals that are added by the drillers. It also must be stripped of contaminants it picks up while underground: bromides, chlorides and some heavy metals. The industry estimates that 70 to 90 percent of the time captured water is reused in another well. However, a small portion of the remaining water is trucked out of state to deep-injection wells, and the rest is diluted and released by treatment facilities into the state's rivers and streams.

But when the coupling failed at Atgas 2H, the water simply came gushing too fast for Chesapeake's operators to bring it under control and collect it. Making matters worse, days of steady rain had partially filled the containment pits and they quickly overflowed, according to preliminary reports. Berms, which are required to be constructed around all of Pennsylvania's 3- to 5-acre drill pads like Atgas 2H, also failed to stem the flow, allowing the fracking fluid to escape into the environment.

DEP authorities are still mopping up at the well and have not yet determined what, if any, long-lasting environmental consequences there may be. A team of drill site emergency responders was able to contain the spill to the drill pad by Wednesday evening. But it's unclear how much water escaped before that. At least some of it is believed to have found its way into nearby Towanda Creek. State officials are testing water along the creek as well as the water in area residents' wells, and they have also warned neighboring farmers to stop their cows from drinking surface water for the time being. So far local emergency officials say there's no evidence of harm to the area's fish and vegetation.

However, investigators did not immediately disclose the chemical makeup of the fracking fluid that escaped, and the formula varies from company to company and from well to well. Though water makes up more than 90 percent of frack fluid, the water is highly salty, and several of the chemicals the industry uses are known or suspected to be carcinogenic or linked to birth defects though prolonged exposure. If initial estimates are accurate, it would make Wednesday's incident the most serious fracking accident in the history of Marcellus Shale development.

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